22 ASTRONOMY • MARCH 2020
Now astronomers can
observe f ledgling stars in
gaseous nebulae as they
emerge from their birth
cocoons. They can watch the
hottest of these stellar youths
excavate cavities in their sur-
roundings and erode dust-
filled pillars where new stars
are trying to form. In the
nearby Orion Nebula, Hubble
revealed protoplanetary diskssurrounding dozens of baby
stars. These dusty disks
appear to be the raw material
nature uses to create planets.
When Hubble launched,
scientists counted only nine
planets in the universe. (This
was before Pluto’s demotion
to dwarf planet status in
2006.) Since the early 1990s,
astronomers have discovered
more than 4,000 planetsorbiting other stars. Although
the space telescope contrib-
uted only a handful to this
total, its spectrographs have
analyzed the atmospheres of
several exoplanets. Perhaps
most intriguingly, Hubble
has detected significant
amounts of water vapor
on a few of these worlds.
The lives of stars play out
over millions, billions, andOne of the Milky Way’s premier
star factories is the Carina Nebula
(NGC 3372), which came to life about
3 million years ago when stars first
ignited in a cloud of molecular
hydrogen. In this view, jets of gas
erupt from infant stars emerging
from their birthplaces. NASA/ESA/M. LIVIO
AND THE HUBBLE 20TH ANNIVERSARY TEAM (STSCI)Hubble has made several
discoveries in our solar system,
including four of Pluto’s five moons.
Pluto and previously discovered
Charon lie in the less-exposed
vertical bar, while Hydra, Nix,
Kerberos, and Styx appear as
fuzzy blobs to either side.
NASA/ESA/M. SHOWALTER (SETI INSTITUTE)Astronomers nicknamed this
planetary the Butterfly Nebula
(NGC 6302) because it looks like the
beautiful insect through earthbound
telescopes. Such objects are the
death shrouds of stars like the Sun,
which will reach this stage in
5 billion years or so. NASA/THE HUBBLE
SM4 ERO TEAM