Tag Archives: exoplanets

55 Cnc e: 0.74 day period, 8.57 Mearth, 1.63 Rearth, *11* g/cm^3!

The exoplanet 55 Cnc e may get its period and mass revised downward due to recent observations that support a paper from last year.

In short, we thought it had a period of 2.8 days and a minimum mass of 14 Mearth.  This is from radial velocity measurements.  The paper from last year, however, made the case that this period may be due to aliasing in the data.  If the planet has a period closer to 0.7 days, it could appear to have a 2.8 day period in radial velocity observations.  And if its period is 0.7 days, then there’s a really good chance that it could transit its star.

Which, it turns out it does.  These new observations confirm it has a 0.74 day orbit, and that it’s mass is much lower: 8.5 Mearth.  But because it’s transiting, we can much more accurately determine its radius: 1.63 Rearth.  This gives it an average density of 11 g cm^-3.  For comparison, that makes it twice as dense as the Earth or Mercury.  For further comparison, that iron meteorite we had at our Physics Fair table (just to the left of Veselin’s laptop in the picture) has a density of roughly 7.5 g cm^-3 and weighs 24.5 lbs.  It was roughly the size of a large dog’s head. If it were a chunk of 55 Cnc e, then it would weigh 36 lbs., roughly a third heavier.

Physics Fair 2011 Astrobiology Table. The iron meteorite in question is to the left of the laptop.

Detecting rings around exoplanets

Figure 2 from "Detectability of planetary rings around an extrasolar planet from reflected-light photometry"
Figure 2 from "Detectability of planetary rings around an extrasolar planet from reflected-light photometry"

Just saw this on astrobites.com: Could Rings Exist Around Kepler “Warm Saturns”?

It’s a new paper on arxiv.org that follows a couple of older papers that try to pin down the detectability of rings around exoplanets.  In this case, the authors are focusing only on planets and candidate planets detected by Kepler.  Astrobites does a good job of summing up the paper, so I’ll just provide a couple of other quick-read papers and a book reference if you’re interested in learning more.

Transit Detectability of Ring Systems Around Extrasolar Giant Planets
Detectability of planetary rings around an extrasolar planet from reflected-light photometry
Planetary Rings

This latter reference, a book from the Cambridge Planetary Science series, is a good introduction to (Saturn’s) rings suitable for undergraduates.

The cost of a newly discovered planet

I get forwarded stuff.  A forward I got today is for a week-old BoingBoing post about Greg Laughlin’s “exoplanet valuation” equation.  Laughlin is essentially trying to find a way to quantitatively compare the importance of each exoplanet discovery.  In this case, he’s trying to put it in terms of dollars and cents.  I don’t see where on his site he does the derivation for the equation, and I haven’t tried running any of the numbers yet (I’m still looking for a complete list of all 1200 new candidates), but the BoingBoing post says that so far:

At the time, the exoplanet Gliese 581 c was thought to be the most Earth-like world known beyond our solar system. The equation said it was worth a measly $160. Mars fared better, priced at $14,000. And Earth? Our planet’s value emerged as nearly 5 quadrillion dollars. That’s about 100 times Earth’s yearly GDP, and perhaps, Laughlin thought, not a bad ballpark estimate for the total economic value of our world and the technological civilization it supports.

The BoingBoing link breaks down the equation, but you can find Laughlin using it everywhere on his blog.

Calling all podcasters!

I mentioned this about a month ago to this list, so I’d like to remind everyone about a great public outreach opportunity.  We’re currently signed up for several slots in the 365DaysOfAstronomy.org podcast.  This is a podcast open to submission from all over the world about any topic of interest related to astronomy.  As such, people from all over the world with hugely varying degrees of expertise download and listen to this podcast.  This is a great opportunity to get involved in public outreach, get your name out in front of the general public, as well as an important addition to your CV or grad school application.  If you’d like to know more about the site and the podcast in general, I suggest reading through their “about” page.

I started doing these as an undergrad at Columbia University.  The grad students there mobilized to establish a “Columbia Mondays” recurring series during 2009.    We did quite a bit of them, and you can find links to all of them from here.  I was thinking we could do something similar for astrobiology at JHU.  We can do podcasts on any topic you like–current events, your research, hobbies, etc–as long as you can link it back to astronomy/astrobiology in some way.  I’ve done about 6 of these myself, ranging from a discussion of the Galileo probe’s discoveries at Jupiter, the science behind detecting moons around extrasolar planets, to an exploration of my interest in the history of astronomy.

Doing a podcast requires writing a transcript, recording yourself reading the transcript, and then uploading everything to the site.  The writing part requires the most time and research, but if we do this as a collaborative effort (someone writes about an area of interest, the rest of us providing copy-edit and revisions) it should go quickly.  Then, using David Coren’s suggestion, we can record and edit the podcast at the Digital Media Center in Mattin in just a couple of hours.

We have four dates reserved on the calendar: Feb 12, April 25, Sept 26, and Nov 28.  The very first one is Darwin’s birthday.  We should do something Darwinian related.  Let me know if you’re interested in doing this first one.  We’ve got to have it submitted February 7th.

Meet with Jim Kasting tomorrow at 10am

Don’t forget that Jim Kasting is presenting tomorrow at 12:30pm as part of the Astrobiology Lecture series at the John Bahcall Auditorium, STScI.

We’ve been given the opportunity to meet with him before his presentation at 10am in STScI room 311. If you’re interested, reply to the list or drop me a line because we need to let Daniel Apai know if there’ll be more than 4 of us.

Here’s one of his papers on arxiv.org: “Exoplanet Characterization and the Search for Life.”

James Kasting’s Astrobiology Seminar this Friday at STScI

From the Astrobiology Lectures listserv comes this announcement for Friday’s astrobiology lecture at STScI:

Friday, December 10, 2010 at 12:30 p.m. in the John Bahcall Auditorium – STScI (Light lunch provided and discussion at 12:00 p.m., talk at 12:30 p.m.) For more information see http://astrobiology.stsci.edu

Speaker: James Kasting, Penn State University

Abstract: Over 400 planets have been found around nearby stars, but none of them is thought to be at all like Earth. The goal now is to identify rocky planets within the habitable zones of their stars and to search their atmospheres spectroscopically for signs of life. To do this, we need new space-based telescopes such as NASA’s proposed Terrestrial Planet Finders or ESA’s Darwin mission (all of which are indefinitely postponed at the moment). If spectra of extrasolar planet atmospheres can be obtained, the presence of O2, which is produced from photosynthesis, or O3, which is produced photochemically from O2, would under most circumstances provide strong evidence for life beyond Earth. But “false positives” for life may also exist, and these need to be clearly delineated in advance of such missions, if at all possible. I will also contrast my optimism about the search for complex life with the more pessimistic view expressed by Ward and Brownlee in their book, Rare Earth.

Webcast & Telecon Information:
We will webcast this talk via streaming video. Please make sure that your computer has RealPlayer, Windows Media Player, or VLC configured. For further information, please visit our website: astrobiology.stsci.edu.

Note that we also provide a telecon access to the talk: we recommend using this phone connection over the audio feed from the streaming video for its higher quality, robustness and possibility for participation in the discussion.

If you plan to connect, please send your phone number to apai@stsci.edu at least a day prior to the meeting.

Reminder: Please help keep the Bahcall Auditorium clean. Thank you.

Astrobiological Factors in Exoplanet Exploration Strategies

We’ve got another lecture in the STSci Astrobiology Lecture Series coming up tomorrow!  This month the lecture will be by Wes Traub from the Jet Propulsion Laboratory at Caltech.  It’ll be in Mudd 100 at 12:30pm tomorrow. The lecture is entitled “Astrobiological Factors in Exoplanet Exploration Strategies.”  The abstract:

What is the best strategy for finding signs of life beyond the Solar System? Until recent years this was a purely philosophical question, but today we have the technical ability to search for signs of life on exoplanets around nearby stars, so the question is now a practical one. To start, we ask what kind of signs of life should we be looking for, and where should we be looking? Next we might ask about the methods we could use for such a search, and the kinds of evidence that we expect to obtain. Finally we can ask about the prospects for starting this search in the coming decade.

After the lecture, the Astrobiology Club gets to meet with Traub at 3pm in Mudd 128. Don’t miss out!