A New Type Ia Supernova in M82

Just a couple of days ago, a dim, but quickly brightening, supernova was discovered in M82, the beautiful "cigar galaxy." At "only" 12 million light years away, this is the nearest supernova to Earth since 1987 and the nearest Type Ia supernova since 1972. With the enormous changes in our imaging technology since then (including the launch and subsequent improvements to the Hubble Space Telescope), this is a fantastic opportunity for precision measurements of one of the brightest and most mysterious explosions in the universe.

The new supernova in M82, discovered by students at the University College London
Observatory.  Photo by Adam Block/Mount Lemmon SkyCenter/University of Arizona

Discovering more about the nature of Type Ia supernovae has been one of the primary goals of the CANDELS project. These supernovae begin as stars like our sun, which have shed their outer layers at the end of their lives and become white dwarfs. White dwarfs are the extremely dense cores of a burned-out star, and although they're only the size of our earth, they have the mass of our entire sun.  The detonation happens when a nearby star adds even more mass onto this dwarf -- when the weight becomes too much, nuclear fusion ignites it and a supernova occurs.

In CANDELS, we study the most distant Type Ia supernovae that we can find, the farthest of which stands at over 10 billion light years away. Our supernovae tell us about the early expansion of the universe (and its Dark Energy), the chemical evolution of the universe, and how quickly supernovae form and explode around 8-10 billion years ago -- at the peak of star formation in the universe.

This nearby galaxy offers a completely different, and rarer, perspective. In 1972, when the last Type Ia supernova this close to Earth exploded, it was still a year before anyone proposed the idea that these supernovae were formed in binary star systems. It was 12 years before someone realized that both stars could be white dwarfs, and 18 years before supernovae could be studied from space with the Hubble Space Telescope. It was over 25 years before such supernovae were used to discover that Dark Energy was accelerating the expansion of our universe.

Motivated by the knowledge and technology gained since the last close Type Ia supernova went off, scientists will be asking an entirely different set of questions this time around. First, we'll be looking for a giant companion star that could have fed mass onto the white dwarf. If a companion star is visible, this would be the first direct evidence that a system with one white dwarf can lead to a supernova; if a companion star is not found, the theory that two white dwarfs can make a Type Ia supernova will gain credibility.

Artist's conception of the single-degenerate (one white dwarf)
theory of Type Ia supernova explosions, wherein
a white dwarf accretes mass from its companion
star.  (original) © ESA and Justyn Maund (Queens Univ. Belfast)

Artist's conception of the double-degenerate theory
of Type Ia supernova explosions, in which two white dwarfs merge
together as they emit gravitational waves. (original) © NASA,
Tod Strohmayer (GSFC),  and Dana Berry (Chandra X-ray Observatory)

Second, scientists will be studying the geometry of the supernova from the fraction of polarized light emitted. Polarization, the orientation of a light ray's electric field, is entirely random when it originates from a spherically symmetric star. However, if one side becomes longer than the other, the light's polarization will have a preferential direction that can be measured on Earth. As the outer layers of the M82 supernova expand, they will become transparent and expose the inner material. Over the next month, scientists will be able to measure the shape of different layers and examine the three-dimensional explosion. With this structural information, we'll learn more about how supernova detonation occurs; specifically, how nuclear fusion begins and spreads through the layers of the white dwarf.

The location of M82 on the night sky from Sky and Telescope.
A more detailed chart is available here

Lastly, Type Ia supernovae are nearly uniform in brightness, serving as excellent distance indicators for most of the visible universe. CANDELS supernova principal investigator Adam Riess -- among others -- will be measuring the distance and doppler shift velocity (the reddening of its light) of this supernova to determine how fast the local universe is expanding -- and infer the amount of the mysterious Dark Energy that surrounds us.

This supernova is particularly rare in that it offers opportunities not only to scientists, but for anyone with access to a dark night sky. It will brighten for approximately a week and a half, and at its peak it will be visible near Ursa Major (the Big Dipper) to anyone with a set of binoculars. Although it's impossible to predict when the next close supernova will be, I'm looking forward to seeing an exploding star with my own eyes - it may be 40 years before there's another opportunity.

223rd AAS Meeting in Washington, D. C.

Twice a year, the American Astronomical Society holds professional meetings covering a broad range of research and education topics. This January’s meeting was held in Washington, D. C. at the National Harbor. I wouldn’t be surprised if it broke previous attendance records, with almost 3200 people on the official registration list. 

Rachel Somerville giving the Heineman Prize Lecture.
Photo credit: Joson Images/ AAS

CANDELS scientists had a very strong representation at this meeting. Rachel Somerville won the Heineman Prize and gave a lecture entitled, “The Formation of Galaxies and Supermassive Black Holes: Insights and Puzzles.” Meanwhile, Jennifer Lotz held a press conference on the release of data from a new ultra-deep, wide-field imaging survey that she is leading known as the Hubble Space Telescope Frontier Fields (see the image from their press-release below).  There was also a CANDELS special session which included 4 talks and 10 posters on CANDELS results, as well as 22 other CANDELS-related talks and poster presentations throughout the course of the meeting.

HST Frontier Field Abell 2744.  Image credit: NASA,
ESA, and J. Lotz, M. Mountain, A. Koekemoer, and
the HFF Team (STScI).

People go to the AAS for a variety of reasons. As one of the largest gatherings of astronomers, it is impossible to see every science talk of interest. For this reason, I find AAS meetings are more of a place to have discussions with your colleagues and the larger astronomical community about priorities and goals for the future. Many of these larger, community-oriented discussions take place during “town hall” sessions.  Sometimes difficult decisions need to be made, especially in the current funding climate. At this meeting, astronomers grappled with the likelihood that many of our beloved facilities will either need to find private partners to sustain operations costs, or be shut down in the next couple years. This is because NSF does not have the money to fund them while continuing forward with important projects like the James Webb Space Telescope and the Large Synoptic Survey Telescope. If you know anyone with a few hundred thousand dollars to spare, you can buy yourself some quality time on top-notch facilities!

Other important discussions include networking with more senior astronomers, especially when you’re on the job hunt. Jon Trump wrote about this aspect of AAS in a previous post.  However, the largest growing demographic at these meetings is young student researchers. This is a great place for them to showcase their work and gain experience talking with people about their research. For me, this was my first AAS meeting where I was on the “other side”, serving as faculty advisor to an undergraduate student who is applying to graduate school this year. As my first thesis student, I encouraged her to come present her results, while I tried my best to introduce her to people doing exciting science as well as folks on various graduate admissions committees. The AAS can be a bit daunting to newcomers, so it’s the advisor’s role to help facilitate discussion and provide a role model for students just starting down this career path.

Neil deGrasse Tyson at the AAS.
Photo credit: Joson Images/ AAS

In addition to science talks, there were a number of sessions on astronomy education research, which is another growing aspect of the AAS community. One session I attended on how to improve student outcomes in Astro 101-style courses, was standing room only. It’s great to see so many professional astronomers care so deeply not just about their personal research, but also about how to improve their approach to teaching science to non-science majors. While this is a significant part of many of our jobs, it may surprise readers to learn that most of us were never trained as teachers. Therefore, these sessions are particularly important for learning how to be effective instructors.

Astronomers also like to have a bit of fun in these meetings. At this meeting there was a special talk by Neil deGrasse Tyson, who was surrounded by hundreds of adoring, geeky fans (a.k.a, professional astronomers) as he talked about how to use twitter to engage the public in science. There was also the infamous AAS “after-party”, which was a bar-hopping extravaganza, complete with astro-themed cocktails and a mechanical bull (although I never did see anyone attempt the bull)!

Space Shuttle Discovery at the National Air and Space
Museum.  Photo credit: E. McGrath

Finally, with the meeting being held in Washington D. C., I took advantage of the opportunity to do some astronomy-themed sightseeing. I visited the National Air and Space Museum hangars located near Dulles airport, where I got to behold the impressive Space Shuttle Discovery, as well as a Mars Pathfinder prototype. The shuttle was even more impressive in person than I could have imagined—definitely worth a visit next time you're in D. C.

Project Astro Kick-off at Donaldson Elementary School

Like last year, I and many other astronomers around the US are participating in Project Astro. Project Astro partners a teacher with an astronomer. We introduced Project Astro in this previous blog post and told you about the workshop that is held at the beginning of each new school year at the National Optical Astronomy Observatory in Tucson, Arizona. In short: The goal is for the astronomer to help the teacher to bring astronomy and science closer to the children in the classroom. Various activities support this goal.

This year, I am partnered up with Donaldson Elementary School's 4th grade classes. Donaldson Elementary is a public school in the North West of Tucson, Arizona. Each of its 4th grade classes consists of about 30 children. Last week, I visited the 2 classes for the first time. When I entered the class room, the children looked at me with big, excited eyes. As a welcome present they had prepared a book for me with drawings of what they think a female astronomer/scientist looks like. It was really touching and their art work was great. Their female astronomers came in all shapes and sizes and forms and colours. I particularly liked the one that put me on the moon!

What does a female scientist/astronomer look like? Here are a few example images of what the children thought before meeting me. Image credit: Janine Pforr, drawings from Donaldson Elementary 4th grade pupils.

We started off with just a general question and answer session, so the children could get to know me a little better and ask anything they wanted to know. One hand after another shot up. And boy, did they ask tough questions! For example: "What's left after a Supernova?" or "How did the Universe start?" or "How long can a person live in space?" or "What is the biggest star?" (You can check for a list of the largest known stars here, they are nearly 2000 times larger than our Sun). It was great and I was really impressed with their sheer endless curiosity.

Phases of the moon. Try to find the right order!
One solution is below, but no early peeking!!
Image Credit: "The Universe at your Fingertips"
and the Astronomical Society of the Pacific.

After that, we started our first activity, the phases of the moon. At the outset I had every child draw how they see the moon. Some drew full moons, some half-moons, some crescent moons. All had craters on them. Some added aliens and the American flag and the moon lander module. We discussed how everyone's drawing looked different and then I distributed little cards that have different moon phases on them, which the kids had to order. Naturally, most of them ordered the pictures from smallest crescent moon to full moon, thus creating half a cycle. The pictures however showed a full cycle. By drawing their attention to the details in the pictures, i.e. craters and mares, I had them rethink their choice and order. With a little help all of them managed to get the order properly and we talked about how often the moon cycles through its phases in a year and how long one cycle roughly is. Next time, I think we'll talk about what causes the moon phases and the seasons.

That day, the kids were very sad to see me leave, but I am sure we will have a great next visit.

With all the curiosity and interest of the children during my first visit, I have to say that I had one special highlight of the day. During recess, one of the little girls came up to me and asked if I was a scientist, which I confirmed. And then she said she wanted to become a scientist, too, when she was grown up. I thought that was very sweet and also exactly what many of us want to achieve with outreach events like this. We want to interest more children in astronomy in particular and science in general and encourage young girls especially that math and engineering and science is for them, too. 

One possible solution for the right order of the moon phases. Image Credit: "The Universe at your Fingertips" and the Astronomical Society of the Pacific.

The Geminid Meteor Shower

We may be in the grip of some Arctic weather here in the US right now, but if you can stand to venture outside then the skies have a treat in store this week, in the shape of the Geminid meteor shower. Hyped as the best meteor shower of any given year, the Geminids reaches its peak this weekend (13/14 December).

So what is a meteor?

They’re also known colloquially as ‘shooting stars,’ but have nothing to do with stars. A lot of things in astronomy that are basically the same are given different names depending on how and where we see them. Space debris is no different. A small, solid body moving within the Solar System is known as a meteoroid. If that meteoroid happens to cross paths with the Earth, it burns up in the atmosphere, creating the distinctive streak that we know as a meteor. In exceptional cases, a large rock might not entirely burn up, and survives intact to hit the ground. The solid remains that hit the Earth’s surface are known as meteorites.

Space is full of debris. A quick look at the crater-covered moon is a good indicator of what the Earth might look like if we didn’t have the atmosphere to burn up most of what might impact us, and erosion on the ground to smooth over the damage caused by those that do. On any clear night, if you watch a patch of sky for long enough, chances are you’ll see a meteor.

What makes meteor showers different to these random occurrences is that they’re highly concentrated – a lot of meteors all originating in the same place – and that they occur regularly, at the same time each year. This is because the Earth is moving through space as it orbits the Sun, carving out the same path every year, and so at the same time each year we hit the same particularly intense patches of debris.

Most of these debris patches have been left by comets. Comets have been observed for as long as astronomical observations have been recorded, and often viewed as divine messengers or omens. One of the earliest recorded sightings was in China in 240BC. The same comet was also recorded by the Babylonians and in medieval Europe, and is even featured on the Bayeux Tapestry. It wasn’t until 1705 that Edmund Halley realised these sightings were of the same object: it now bears his name, Halley’s Comet, and is due to pass the Earth again in 2061.

Comets are small bodies made up of ice, rock and dust, thought to originate in the outer reaches of the Solar System. Some of these ‘dirty snowballs’ are pushed towards the centre of the Solar System, where they enter into highly elliptical orbits that see them pass close to the Sun before shooting off back to the outer reaches of the Solar System. As they approach the center of the Solar System, radiation from the Sun causes some of the material in the comet to melt and vaporize; this gives rise to the characteristic tail. Consequently, the tail always points away from the Sun.

Forging paths through the entire length of the Solar System is dangerous work, and not all comets survive the journey intact. In 1994, Comet Shoemaker-Levy 9 collided spectacularly with Jupiter. More recently, you may have seen Comet ISON in the news as it ventured into the inner Solar System. ISON made its closest approach to the Sun (called perihelion) on November 28^th 2013, but is believed to have disintegrated as it whipped around the Sun.

Those that do survive their journeys, however, are not good at cleaning up after themselves. There are still debris trails from several comets that have crossed the path of the Earth’s orbit in the past, and each time the Earth reaches that point in its orbit – once per year – we collide with this debris, which burns up in the atmosphere to produce the streaks of light we call meteors. Comet Halley mentioned above actually intersects the Earth’s orbit twice, and its trail is believed to give rise to both the Eta Aquarids in May and the Orionids in late October.

The Geminids are unusual for a meteor shower in that the origin is not actually a comet, but an asteroid known as 3200 Phaethon. The asteroid is on an unusual orbit that brings it closer to the Sun than Mercury, and it sheds enough material to generate the most intense meteor shower of the year. The video below from NASA Science Casts explains more about the origin of the Geminids.

           

Meteors can be seen all over the sky, but most will appear to originate at a single point, known as the radiant. For the Geminids, this radiant is in the constellation Gemini (which gives the shower its name), close to the star Castor. This effect is caused by the fact that the Earth is moving into the debris; this is the same effect used to demonstrate spaceships moving at faster-than-light speeds in science fiction.

The Eastern sky as seen from Austin, Texas at 9pm on Friday December 13th 2013.
The Geminid meteors appear to radiate from the constellation Gemini, near to the
star Castor. Gemini can be most easily located by finding Orion with its distinctive belt.
A little way over Orion's left shoulder (the red star Betelgeuse) are the two bright
stars Castor and Pollux. (Image credit: Stellarium)

The Geminid meteor shower will peak on Friday and Saturday nights (December 13^th – 14^th), but meteors can be seen for a few days either side. The best thing about meteor showers is that no equipment is required (save something to keep you warm) – just pick a dark location and lie back so that you can see as much of the sky as possible.

The Geminids regularly peak in intensity around mid-December and seem to have increased in strength in the past years. This year, astronomers expect 120-160 meteors per hour during the peak, which would be early in the morning on Dec. 14. However, the moon is close to  full during the peak so only the brightest meteors will be easy to spot. For the truly dedicated, the best time to watch is an hour before dawn, when the moon will have set leaving the sky much darker. Reports say that we can still expect around 50 per hour under the best observing conditions (clear skies, no light pollution, etc.) and we may even be able make out their different colors (mainly white and yellow and a few being blue, green or red).

And if you’re not brave enough to venture out into the cold, you can even watch online. Now that’s astronomy for the 21^st century.

Astronomer of the Month - Benjamin Weiner

Each month we will highlight a member of the CANDELS team by presenting an interview introducing them and what it's like to be an astronomer. This month's Astronomer is Benjamin Weiner.

Benjamin Weiner at Las Campanas in Chile

Tell us a little about yourself!

My name is Benjamin Weiner.  I'm an Associate Astronomer (research scientist) at Steward Observatory, which is the Department of Astronomy at the University of Arizona, and operates several mountaintop observatories. I was born in California but grew up in Pittsburgh.  I went to Swarthmore College, took a couple of years off, then got a PhD in physics/astronomy from Rutgers. I have lived in Pennsylvania, Massachusetts, New Jersey, California (both halves), Maryland and Arizona. Away from work I like to spend time hiking, running, and riding my bike.

What is your specific area of research? What is your role within the CANDELS team? 

I work on several different projects -- the one most closely related to CANDELS is the nature and properties of star-forming galaxies at redshifts 1-2, 7-10 billion year ago, essentially adolescent galaxies. By "nature" I mean we try to figure out what is the amount of gas and stars in these galaxies, how fast are they forming stars, what are the velocities of the gas - are they rotating like the Milky Way disk or more chaotic. I also study the winds (gas outflows) driven by galaxies and the link between galaxies and the circumgalactic gas probed by quasar absorption lines.  And the properties of dwarf satellites of low-redshift present-day galaxies.  I have also built instrumentation for ground-based telescopes, and software for reducing data.

Within CANDELS my role is to lead the data reduction and science efforts from the grism spectroscopy observations that we do with Hubble. The main goal of these observations is to get spectra of distant supernovae and their host galaxies, but we also get spectra of other galaxies in the same field.

What made you want to become an astronomer? At what age did you know you were interested in astronomy? 

I was interested in astronomy as a grade-schooler, although since I grew up in a city, didn't really get a good look at the night sky very often unless we went out of town -- I have a distinct memory of being wowed by a clear night sky with many stars when I was about 16, from a small town in Pennsylvania. I remember borrowing a small telescope from my high school physics teacher, and us trying to photograph a partial eclipse. Also of the Pennsylvania Governor's School for the Sciences summer school taking us to the Allegheny Observatory where we got to look at Saturn through a pretty big telescope. Even with pictures from space probes, there is no substitute for seeing the thing directly. However, I did physics in college, not astronomy, and didn't really seriously consider astronomy until my first year in grad school, when I was less motivated by the physics classes. My friend Julianne  suggested, "You should try astronomy, it's more interesting and easier." So I did.

What obstacles have you encountered on your path to becoming an astronomer and how did you overcome them? 

When I started really doing research, rather than taking classes and doing homework, I worried about having to create my own new projects and problems to work on. It turns out that wasn't so hard. It's much harder to manage all of the projects and to know when to declare one "good enough," finish it, and move on.

 

Who has been your biggest scientific role model and why? 

I have never really identified people as role models, but one of the astronomers I learned the most from, just from informal talking, is Steve Shectman. I admire Vera Rubin's persistence and enthusiasm, George Preston's humor, and Jim Peebles's graciousness to younger people.

What is it like to be an astronomer? What is your favorite aspect? 

My favorite aspect is that we get to engage our curiosity, and that we have to confront whatever it is that the universe has decided should be physical fact. We can try to construct ideas or test certain theories, and sometimes they're right, but often nature just doesn't work the way we expect or throws us a surprise.

My less favorite aspect -- aside from the office politics that go with any job -- is that for a discipline that grew from staring at the sky, we spend an awful lot of time inside, under artificial lights.

What motivates you in your research? 

I like the challenge of figuring out original ways to design observations or studies to understand astronomical objects or test models. We can't do traditional lab-style  "experiments" in astronomy since everything is far away, so you have to measure effects with what nature allows you to detect. And sometimes a clever observational design means you don't need the biggest telescope or the most resources.

What is your favorite astronomical facility? (This could include telescopes or super computers, for example) 

Benjamin Weiner walking up to the Magellan Telescopes
at Las Campanas in Chile.

I like going to the telescope, which for me is the most romantic, and also most scenically beautiful, part of doing astronomy. It's hard to pick one favorite, but some of mine are the observatories at Las Campanas in Chile, the VLA in New Mexico, and the MMT on Mount Hopkins here in Arizona. I would really like to visit Antarctica someday but don't currently work in the areas of astronomy that would get me there.

Where do you see yourself in the future? What are your career aspirations? 

Right now I'm mostly doing research on relatively short-term projects, but I would like to do more teaching or outreach and work on a longer term project, possibly a telescope or a survey. Both of those are planning to build things for the future, more so than hopping from one project and grant proposal to the next.

 

If you could have any astronomy related wish, what would it be? 

I'd like to be able to see up close and in detail some of the things we study -- a supermassive black hole's accretion region, or a distant galaxy, who wouldn't?  But astronomy is not just a collection of objects, but a system of knowledge created by people, and if I could have one wish it would be that those people behave more decently to each other.

If I could have a second wish it would be that our society would value education, research, and knowledge more highly.

 

What is your favorite, most mind-boggling astronomy fact? 

 

That we can deduce anything at all about the nature and physics of stars, gas, dust, galaxies -- even planets around other stars -- that are so far away and that we'll never be able to touch or see in any more detail. Much of what I do is spectroscopy, and it's always hard to explain because it doesn't make pretty pictures. In 1859, Kirchhoff and Bunsen used the then-new spectrograph to show that the Sun was made of the same elements that exist on Earth. It both blows my mind that we can know that, and that we've only known it for 150 years.

Is there anything else you would like for the public to know about you or astronomy in general? 

I wish we could better communicate how science is imperfect, but generally correct or workable, especially in the long run. I think the popular conception of science is too biased toward lone geniuses making huge discoveries and overturning all of what was known before. In reality we make much slower progress, and "scientific revolutions" are based on a slow accumulation of facts and ideas that gradually build a new consensus. Even Einstein was no Einstein; he built on the work of people before him and discussed many ideas with his contemporaries.

Science doesn't know or predict everything, but the consensus is usually pretty damn reliable, especially for well studied subjects. You have to understand that science can be imperfect and largely reliable at the same time, otherwise you fall prey to hucksters claiming that scientists have got it all wrong and are covering it up. Anti-evolutionists, quack medicine scammers, and climate change denialists use these arguments, which are based on misrepresenting how science is an imperfect process that nevertheless produces useful results.

I'm concerned that an easily distracted culture that values only short term returns isn't supporting the resources and education we need to build a long-lasting healthy society.  For example, the Pennsylvania Governor's School that I mentioned going to many years back, was cancelled several years ago due to state budget cuts. It was just revived through heroic fundraising and donation efforts by some dedicated alumni. But that's not a long term solution.  The society at large, through the state, needs to make it a priority to have an educated population, to value the work of teachers and people who create knowledge. Education takes people and facilities and you just can't build a stable program by cheaping out or depending on charity every year.