Showcasing the Possibilities of Multiwavelength Science

HST and SOFIA are embarking on a joint program that focuses on the beginning and the end of stellar evolution.

In 2020, two joint Directors' Discretionary pilot programs were approved to showcase the possibilities of multiwavelength science with the Stratospheric Observatory For Infrared Astronomy (SOFIA) and the Hubble Space Telescope (HST). These programs, formed out of a partnership between STScI and USRA, focus on the beginning (PI: Karnath) and end (PI: Goldman) of stellar evolution.

We encourage everyone to take full advantage of these publicly-available datasets. We expect all observations to be complete by early 2022. Information on the status of these observations can be found below. 


Joint Observations 

SOFIA and HST Multi-wavelength Study of the Symbiotic Mira HM Sge

PI: Steve Goldman (STScI)

Hubble WFPC2 narrowband image of HM Sge
Previous Hubble WFPC2 narrowband image of HM Sge (F502N) of the [OIII] molecular line at 500 nm.

HM Sagittae is a symbiotic binary system composed of a cool Mira variable and a hot white dwarf companion, separated by ~60 au. We expect the hotter star to be accreting material from its cooler companion. While the accretion details are uncertain, the mechanism in symbiotic Mira systems is thought to be Wind Roche Lobe Overflow (WRLOF). What makes Hm Sge unique is its relatively recent (1975) outburst, where it brightened six orders of magnitude in the optical, and remained bright for longer than the expected few days. We are probing this source in the UV and IR with four instruments to study its dynamics and characterize its long-term evolution as it continues to relax decades after its explosion. This data will give us insights into a range of astrophysical phenomena of great interest to the stellar community.

Read the Whitepaper


HST Program 16492
SOFIA Program ID: 75_0057
  • Program details
  • FORCAST Observations anticipated: July 2021

  • EXES Observations anticipated: December 2021

HM Sge is also a part of a monitoring campaign by the American Association of Variable Star Observers (AAVSO).


Observatory Instrument

Wavelength Regime

Observation Type Filter
HST (2 orbits) COS


Spectroscopy G140L/80 G230L/2950
HST (2 orbits) WFC3


Narrowband imaging F656N(Hα) F658N ([N ii]) F502N ([O iii])
SOFIA (3 hours) EXES


High-resolution spectroscopy 7th – 10th order


Imaging & low-resolution spectroscopy All For_F (12)  FOR_G111 FOR_G227



Investigating the Outflows and Shocks of HOPS 361

PI: Karnath (URSA/SOFIA)

HST WFC3/IR F160W image from 2009 identifying the outflows and protostars in NGC 2071. The blue arrows identify the outflow directions from two protostars HOPS 361-A and HOPS 361-CAB driving the outflows in the region.

Protostellar outflows are an ubiquitous part of the star formation process. They provide a record of variable accretion onto stars, have a significant impact on the surrounding molecular cloud and ISM, may disrupt or trigger star formation in molecular clouds, and can be an important laboratory for understanding the origin of far-IR line emission from outflows. NGC 2071 is a system containing at least two outflows from a small group of intermediate to low luminosity protostars. The shock-excited emission lines in the near- (HST/WFC3-IR) and far-IR (SOFIA/GREAT) are being used to study the energetics of outflows and their impact on the surrounding cloud. The WFC3/IR images of [FeII] and Paschen β lines will trace J-type shocks. Proper motions of the outflow knots will be derived by comparing a 2009 WFC3/IR image with the new observations. The SOFIA/GREAT [OI] line at 63 microns and four additional CO transitions will trace shock heated gas providing radial velocities of the shocked emission as well as measurements of the mass flow and heating by shocks and UV radiation. Together, the HST and SOFIA data will measure 3D space motions of knots and quantify mechanical feedback from accretion driven outflows to provide one of the most detailed measurements of the feedback from a system of protostars to date.

Read the Whitepaper


HST Program 16493
SOFIA Program ID: 75_0056




Wavelength Coverage

Observation Type


SOFIA (3.3 hrs)




491-635 GHz (4G1), 890-1092 GHz (4G2), 1240-1525 GHz (4G3), and 2490-2590 GHz (4G4)

HST (12 orbits)



Narrowband imaging

F126N, F128N, F130N, F164N, and F167N



HST Help Desk 

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