World Science Festival in NY

As many of your probably already know, the World Science Festival is going on now. While there are lots of very interesting (but somewhat expensive for a family) talks and lectures, there are two free events which are interesting and fun:

1. The science fair in Washington Square Park on Sunday July 6th
2. The full scale model of the James Webb Space Telescope (JWST) currently on display at Battery Park (read about it here). NASA ships this out to various conferences and meetings, and is really impressive (yes, they are going to launch something that big into space on a rocket - not a shuttle.) JWST is one of the biggest projects going on in astronomy today (esp. space-based astronomy). To learn more about it, listen to this interview with Dr. Mark Clampin of NASA.
   

Enjoy, and I really hope to be posting my interviews soon!

Robots. In Space!

Helping the human race! On the International Space Station. Read more here. This article definitely appeals to the Isaac Asimov fan in me.

Watching a blizzard on Saturn

with your help! Go here to read how NASA and amateur astronomers teamed up recently to do exactly that. Quite impressive.

The Exploding Sun

Okay, the Sun is not going to explode itself. But look at these images of violent eruptions on the "surface" of the Sun taken by NASA's new Solar Dynamics Observatory and you might be surprised that it isn't.

Third Annual World Science Festival in NYC

Will be held from June 2 - June 6. It promises to have lots of interesting lectures and events throughout the city (or, at least, throughout Manhattan), go here to keep track of it all. Enjoy!

It's not just a Museum

Scientists at the American Museum of Natural History conduct a lot of research as well. Read below about an instrument they are building for the James Webb Space Telescope, NASA's long-awaited to the Hubble Space Telescope. Enjoy!


A wafer-thin titanium disk, nearly two inches in diameter and punctured with seven perfect holes, will launch into space with the James Webb Space Telescope in 2014. Called a non-redundant mask, this tool filters light coming from very bright objects like stars to dramatically improve a telescope’s resolution for fainter objects. Conceived of on the sixth floor of the Rose Center for Earth and Space at the American Museum of Natural History, this non-redundant mask was described in a white paper submitted to the National Academy of Sciences’ Astronomy & Astrophysics Decadal Survey and will launch in the Canadian Space Agency's Fine Guidance Sensor Tunable Filter Imager on board the James Webb Space Telescope.

“We designed a non-redundant mask for the space telescope late in the Webb project, but it was accepted because it improved resolution by more than a factor of two and is so easy to implement,” says Anand Sivaramakrishnan, chief instrumentation scientist in the Museum’s Department of Astrophysics. “This is not a new technique—it was invented for radio astronomy in the late 1950s and revised for ground-based astronomy in the late 1990s. But this is the first time it will be used in space.”

Sivaramakrishnan and his team designed non-redundant masks for ground-based telescopes like Palomar and Gemini; one such mask is currently assisting the Museum’s Project 1640 to image extrasolar planets on the 200-inch telescope at Palomar.

The new mask for the space telescope was designed using a simple concept. By punching holes in a metal plate, much of the light from a telescope’s primary mirror is obscured. The beams selected by the mask come through to the image, turning an imaging telescope into an interferometer, an instrument that spreads light into a complex fringe pattern that reveals the presence of close faint structure around a bright object.

Non-redundant masks improve a conventional telescope’s resolution by a factor of 2.44 so that objects very close to each other can be resolved in an image. On the ground, the mask enables objects about 100 times fainter than a bright star to be imaged. But in space, a non-redundant mask that is part of an exceptionally stable space telescope should be able to detect objects 10,000 times fainter than the nearby bright object or star. Extrasolar planets can be directly imaged by the James Webb Space Telescope, a large infrared telescope with a 6.5 meter primary mirror, the successor to the Hubble Space Telescope.

The mask conceived of at the Museum for the James Webb Space Telescope is 50mm in diameter. Its seven holes are hexagonal in shape to maximize the amount of light passing through, but they are also smaller than their corresponding mirror segments in order to correct for a potential misalignment of the telescope’s mirror and the mask. Finally, the mask was designed so that none of the telescope’s supporting struts arch across holes.

“Our initial observational targets will be proto-planets and Jupiter-like planets in the constellation Taurus and other nearly stellar nurseries,” says Sivaramakrishnan. “But in addition to planets and faint companions, images obtained with the mask can also reveal regions around supermassive black holes in the centers of galaxies as well as the host galaxies around quasars to see how these incredibly powerful sources affect their environments.”

The “JAM Team,” or the James Webb Space Telescope Aperture Masking group led by Sivaramakrishnan, includes Peter Tuthill and Michael Ireland of the University of Sydney and James Lloyd of Cornell University. The team also counts David Lafrenière of the University of Montreal, Frantz Martinache of the Subaru Telescope, and Rémi Soummer of the Space Telescope Science Institute as members. Barry McKernan and Saavik Ford, both affiliated with the Museum and at the City University of New York, broaden the scientific goals of this masking project to include black holes and quasars. Sivaramakrishnan’s non-redundant masking study is funded by the National Science Foundation and NASA.

It's not just about the Cosmic Microwave Background

ESA's new satellite Planck will also help astronomer learn how star form, as evidenced here. I like general purpose Astronomy satellite.

One small step...

... for the construction of (one of) the next large optical telescope. Click here to read about where ESO hopes to be the E-ELT, the European Extremely Large Telescope, and why that location was chosen. Now to see if it gets built.

Hubble's 20th Birthday

was last month. Happy Birthday Hubble! Go here to get the info.

My take on the definition a planet

As you know (and if you didn't, read the comments on the post below describing Pluto), but there is a legitimate debate whether or not the definition of a planet should be dynamical (orbital parameters, mass, etc.) or geophysical (essentially, is it spherical and orbit a star?) in origin. Personally, I prefer the dynamical view, and find the geophysical view too inclusive. Sphericity means its mass is above a certain value, or that the mergers that produced the object were at sufficient velocity to melt the product such that is cooled into a spherical shape. The number of spherical objects in the Solar System is large, and as a result personally don't feel that should be the primary definition of what makes a planet. It doesn't bother me that Ceres is not taught in schools because, frankly, it isn't that special. It is simply the largest asteroid in the asteroid belt - it is not even the only spherical asteroid.

I prefer the dynamical view because it better incorporates our current understanding of star and planet formation. A cloud of gas and dust gravitationally collapses into a star. As it does so, a thin disk of gas and dust form around the star. Inside this disk, collision between dust particles result in proto-planets, which then coalesce through collisions into planets. These objects are sufficiently massive that, through gravitational interaction, they most "clear" their surroundings of gas and dust - opening a gap in the disk (which has been observed in several systems). The friction inside this disk is believed to lead to circular orbits, but this doesn't have to be the case - as recent observations of exoplanets indicate (as you point out). This does mean that the objects orbit in the same plane.

If one was to define a planet based on this model for planet formation - which may or may not be the best thing to do - the requirements would be:

(a) "By far" the most massive object in its vicinity, a signature of the object clearing out a gap in the proto-planetary disk in its formation. By this criterion, Ceres would not be a planet because it is located inside the asteroid belt, whose total mass is larger than that of Ceres. The same is true for Pluto. The mass of known objects in orbits similar to that of Pluto is greater than that of Pluto. Note this criterion does not demand sphericity, just that the object is much more massive than the sum of all objects in similar orbits.

(b) The object orbits the same plane as other planets in this system. Now, this is a little tricky formally because it is circular - an object is a planet because it has an orbit like other planets. However, in our Solar System, the orbital plane of Mercury through Neptune varies by only a few degrees. [This is true for objects in the asteroid belt as well, which is the asteroid belt is often called a "failed planet" - it would have merged into a planet if not for its location near Jupiter]. Pluto's orbit, and that of the other massive spherical KBOs, is far off the ecliptic.

This definition is far from perfect, but I personally feel it better represents our current understanding of planet formation. Admittedly this is not the official IAU definition, but the official IAU definition incorporates these two elements. This definition is also general enough that it incorporates many of the "odder" exoplanets you mention - the ones with high eccentricity, the giant planets very close to their star, the planet that orbits its star backwards. As more exoplanets are detected, and these planetary systems and our own Solar System are better studied, the definition will and should change again. The new IAU definition I believe is a step in the right direction, and Dr. Stern's is a step in the wrong one - I feel that too many objects satisfy this criteria for this designation to have any meaning. This view is shared by a vast majority of astronomers I know (including the ones who study exoplanets and Solar System objects), and I believe that of a majority of astronomers - though far from unanimous as you point out.

And yes, dwarf planet is not a great name. Plutoid is better. I do feel that looking for self-consistency in astronomy nomenclature is futile, because frankly there is none.

Lastly, it is not clear that Pluto satisfies the dynamical (Dr. Stern's - quoted in the comments below) definition of a planet being "any non-self-luminous spheroidal body in orbit around a star." The center of mass of the Pluto - Charon system is outside of Pluto. Also, the gas giant planets radiate more light then they receive from the Sun. Therefore, they could be considered self-luminous, and would also not be considered planets under this definition.

[For those reading the comments below - Hydrostatic equilibrium is when, everywhere inside an object, gravity is balanced by an outward force. This is true for all stable objects (essentially by definition) - spherical or not.]

What do you think? What is your opinion? Does this make sense? Let me know, I'm genuinely curious.