Hubble's Universe Unfiltered

It is a maxim on Broadway that it takes decades of hard work to become an overnight sensation.

Humor aside, the sentiment expressed is true enough in many fields. It takes years of training, preparation, and journeyman efforts to hone one's craft so that it is worthy of being discovered (although there is no guarantee it will be discovered). It has become popular to call this the "10,000 hour rule": only after about 10,000 hours of practice can you hope to become expert at anything.

I don't know how many hours I've spent doing scientific visualizations, but I've been creating them in various forms for about 20 years. I like to think that my work on Hubble and some IMAX projects has granted me a slice of notoriety, albeit within the tiny, tiny field of astronomy visualizers. Then, along comes Astronomy Picture of the Day (APOD).

On Tuesday, May 14, 2013, APOD featured one of my visualizations. It is a galaxy collision piece I did for Hubble's 18th anniverssary back in 2008. The viz shows a computer simulation of galaxies colliding and compares that to five Hubble observations. The point is to naturally show how each Hubble image is but one snapshot in a collision process that lasts for a couple billion years. Over the past five years, this sci viz has become probably my best-known work, as numerous astronomers tell me they use  it in their classes and presentations. For APOD to feature it seems like old news.

Thing is, APOD did not link to the version on HubbleSite, but instead to a posting I threw up on YouTube. After five years on YouTube, the video had gotten a respectable 28,000 views. Add one day of APOD-induced visits, and that number climbed to 176,000. After another day, it was up to 225,000 and was the #1 Science & Technology video on youtube. I confess to being flabbergasted at such attention to an "old" work. A bunch of astronomy friends, who surely had many chances to see this before, e-mailed me and my collaborators about our cool "new" visualization. It has been gratifying and bemusing at the same time.

One take-away is the significant power of an APOD posting. We've know for a long time that Robert Nemiroff and colleagues posess significant power to sway the internet masses. Now I can give one measure to that power: 200,000 views on YouTube in two days. Wield it wisely, APOD.

Q: Will Hubble Observe the Recent Gamma-Ray Burst?

On April 27, 2013, NASA's Fermi Gamma-Ray Telescope observed a gigantic outpouring of gamma-ray emission in the constellation Leo. Such gamma-ray bursts (GRBs) have been observed by satellites since the late 1960s. Since then, astronomers have painstakingly pinned down that the underlying source is generally a huge supernova explosion in a distant galaxy. A massive star, billions of light-years away, collapses its core to form a black hole and explodes its outer layers across interstellar space. GRBs are the enormously energetic birth announcement of a black hole.

What made GRB130427A special is that it is relatively close, about 3.6 billion light-years away. Closer means brighter, and the gamma-rays observed were described as "shockingly, eye-wateringly bright." It set records for both the highest energy gamma-rays seen by Fermi as well as the longest-lasting GRB. The burst lasted for hours and remained detectable for most of a day.

The duration of the burst allowed astronomers to trigger simultaneous observations from other telescopes in other wavelengths. GRB130427A has been detected in optical, infrared, and radio wavelengths. Astronomers will continue to monitor the burst location to measure how the explosion fades away and observe the expected supernova remnant. A supernova of this strength, located this close, provides enticing opportunities to see details not yet uncovered during other, previous stellar explosions.

Hence, the natural question that I received is whether the Hubble Space Telescope will join in the follow-up observations.

Hubble has been used for follow-up observations to other discoveries many times. For example, ground-based observations uncovered the solar system's most-distant known object, Sedna. But only Hubble's fine resolution could get a decent estimate of Sedna's size. When Hubble can provide important additional information, it may be tasked to observe what are called "targets of opportunity."

Such interruptions to Hubble's schedule do have a cost. Observations are meticulously planned well in advance to maximize the scientific return of the telescope. Given Hubble's orbit around Earth and Earth's orbit around the Sun, some regions of the sky are more efficiently scheduled on a given date. Slewing the telescope to another part of the sky is slow and will impact the research of those who have waited many months for their observations. The important criteria for targets of opportunity is both scientific merit and that Hubble must have a unique capability not provided by other telescopes.

At this time, I am told that Hubble is not scheduled to observe GRB130427A. It is not surprising to me, as the observations most needed now are repeated monitoring visits to the target and Hubble is definitely not designed for daily monitoring. Once the underlying supernova has been found, perhaps Hubble's resolution or ultraviolet light instrumentation might provide a unique capability. If so, I'm sure that some astronomer will propose for such observations.

What the observations of GRB130427A highlight to me is the intense growth of multi-wavelength astronomy and the fluidity of international scientific cooperation in the Internet age. Within hours, quick-response telescopes had joined observations to provide complementary views in wavelengths that record distinctly different aspects of the explosive event. Round-the-clock monitoring requires round-the-world coverage, and observatories joined efforts to provide both in a collaborative campaign that will last for weeks to months. Like Hubble's orbit, science flows freely across national boundaries.

Q: Which is the biggest star out there, if biggest means the greatest radius?

A: The stars with the biggest radii are generally considered to be red supergiant stars. Some folks define a class they call "hypergiants," but most astronomers do not split hairs that finely. On the Hertzsprung-Russell diagram, lines of constant radius run diagonally from upper left to lower right. Hence, stars in the extreme upper right will be the ones with the largest radii. Such a star will have a low temperature (red color) and a high luminosity. To achieve such high luminosity while having a low temperature, it must have a huge surface area — thus, it will be a red supergiant.

Well known red supergiants include Betelgeuse and Antares, but neither is the largest. I don't do stellar research, so I'd have to look up what others say. An article on Universe Today says the largest is VY Canis Majoris (VY CMa), measuring about 1800 times the size of the Sun. A paper by Emily Levesque (University of Hawaii) cautions that VY CMa has a wide range of size estimates, but agrees that the largest stellar radii are about 1500 times the radius of our Sun. The paper lists four such behemoths: KW Sagittarii, Case 75, KY Cygni, and Mu Cephei. If placed in our solar system, these red supergiants would fill space almost to the orbit of Saturn. The entire orbits of Mercury, Venus, Earth, Mars, the Asteroid Belt, and Jupiter are all smaller than the diameters of the largest stars.