Observation Targets and Science for our Flights

FORCAST is the science instrument that will be used on our flights.

OC3-I flights 3 & 5 – FORCAST Observation Targets


[Abstracts of the observing proposals are appended to this file in program numerical order; the “03” prefix means Cycle 3.]

Flight #3 – September 15-16

Leg 4 (30 mins): HIP 70692 = 5 Ursae Minoris (d = 110 pc)

Bright optical star (V = +4.3) for telescope setup & focusing; object # 70692 in the catalog of stars observed by the parallax (star distance) measuring space telescope Hipparcos that operated from 1989-93.


Leg 5 (30 mins): W31S Points 1-2 (d = 4 to 15 kpc)

Program = 03_0008, P.I. = Jim De Buizer (SOFIA staff)

Star-forming region in the constellation Sagittarius; The name means object #31 in the Westerhout catalog of galactic radio sources; the ‘S’ suffix means the southern part of the region. Radio telescopes detect emission from ionized hydrogen (HII) produced by hot, massive young stars. This complex is apparently several star forming regions at a range of distances along the same line of sight:





Leg 6 (45 mins): Beta UMi (Ursae Minoris) = Kochab (d = 40 pc)

Calibrator: bright red giant star:


Leg 7 (27 mins): 2 Pallas = Pallas, 2nd asteroid discovered

Calibrator; large asteroid, strong mid-IR source with no spectral lines:


(d = 0.00000858 pc)
Leg 8 (46 mins): W49A Point 2 (d ~ 14 kpc)

Program = 03_0008, P.I. = Jim De Buizer (SOFIA staff)

Westerhout 49; star forming complex in the constellation Aquila. The ‘A’ suffix labels the ionized hydrogen (HII) cloud within the complex:


Leg 9 (30 mins): W51A (d ~ 4 kpc)

Program = 03_0008, P.I. = Jim De Buizer (SOFIA staff)

Westerhout 51; star forming region in the constellation Aquila

Leg 10 (30 mins): W58A

Program = 03_0008, P.I. = Jim De Buizer (SOFIA staff)

Westerhout 58; star forming region in the constellation Cygnus


Leg 11 (195 mins): Elia 3-18 = Elias 3-18 (d ~ 140 pc)

Program = 03_0064, P.I. = Jean Chiar (SETI Institute)

This object is a low-mass (meaning, approx. solar-mass) protostar with a protoplanetary disk seen nearly edge-on. It is in the nearby Taurus star-forming region mapped by Jay Elias during his doctoral dissertation work at Caltech in the late 1970s.

Flight #5 – September 17-18

Legs 4 &5 (60 mins total): HIP 70692

Optically bright star for telescope setup; see flight #3, leg #4.

Leg 6 (25 mins): 2 Pallas

Calibrator; see flight #3, leg #7.
Leg 7 (128 mins): W3_WR_grism (d ~ 2.0 kpc)

Program = 03_0091 P.I. = John Bally (U. Colorado)

Westerhout 3 star-forming region in the constellation Perseus:


The suffix “WR grism” indicates a particular point in the nebula that the P.I. wants to observe with the FORCAST grism (grating+prism).

Leg 8 (21 mins): IRAS 19306+1407 (d ~ 2.7 kpc)

Program = 03_0079, P.I. = Kathleen Kraemer (Boston College)

This is a late-stage red giant star embedded in a cloud of dusty & gas that it is expelling as it evolves into a planetary nebula. The name means that this object is in the first all-sky far-IR source catalog produced by IRAS = the Infrared Astronomy Satellite in 1983. The numbers are the object’s celestial coordinates (Right Ascencion and Declination).


Leg 9 (35 mins): Beta UMi

Calibrator; see flight #3, leg #6.

Leg 10 (20 mins): V718 Tau

Program = 03_0079, P.I. = Greg Sloan (Cornell)

Variable red giant star of the Mira Ceti type; the name means variable star #718 discovered in the constellation Taurus:




Leg 11: Asteroid 62 Erato (= 62nd asteroid discovered)

Program = 03_0114, P.I. = Margaret McAdam (U. Maryland)




Proposal ID: 03_0008

Principal Investigator: James De Buizer (SOFIA – USRA)

Title: Revealing the Embedded Structures and Sources within Giant HII Regions: The Northern Hemisphere Sample

Abstract: Unlike low mass star formation, relatively little is known about massive star formation. Furthermore, most studies concentrate on the processes of isolated star formation while little is known about clustered star formation, despite the fact that the vast majority of stars are formed within clusters. Giant HII regions harbor the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, the great majority of these GHII regions are optically obscured and far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 19.7 and 37.1um imaging with approximately 3 arcsecond resolution well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. This proposal is designed to catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 20um. Such a catalog is expected to be an invaluable tool for the SOFIA community for follow-up spectral imaging and polarimetric imaging, as well as targeted MIR/FIR spectroscopy of individual sources within these regions.

Proposal ID: 03_0064

Principal Investigator: Jean Chiar (SETI Institute)

Title: The Evolution of Preplanetary Matter: FORCAST Grism Spectroscopy of Ices from 5 to 8 microns

Abstract: The 5 – 8 micron spectral region, which is inaccessible to ground-based telescopes, is important to astrochemistry because it is rich in solid-state molecular absorption features arising in interstellar or circumstellar ices. These features provide a means of evaluating abundances for carriers that include organic species such as methane, formaldehyde and formic acid; moreover, some features are diagnostic of thermal or energetic processing of the ices, and hence provide insight into the evolution of preplanetary volatiles in regions of active star formation. However, data obtained on space platforms to date lack either the required sensitivity and spatial resolution (ISO SWS) or the required spectral resolution (Spitzer IRS) to fully isolate and characterize the absorption profiles over the range of relevant environments. We propose to use the FORCAST grism in cross-dispersion mode to yield spectra with resolving powers an order of magnitude higher than was possible with the Spitzer IRS at these wavelengths. Targets are selected to cover environments ranging from a prestellar core to the vicinities of low, intermediate and high-mass young stellar objects (YSOs). An important advantage of this gain in spectral resolution is the ability to ensure precise separation of solid-state and gas-phase features, crucial for YSOs with circumstellar gas-phase lines. The resulting spectra will allow us to reliably separate blended features and characterize structure in the underlying solid-state profiles with reference to data for laboratory analogs. The observations will provide new insight into the nature of the absorbers in this important spectral region and enhance our understanding of how the ices that form at low temperature in molecular clouds evolve in proximity to YSOs. This proposal was awarded 6.5 hours of time in Cycle 1 (panel evaluation 4.9/5.0) but partial observations of only 2 targets (out of 5) have been completed to date.

Proposal ID: 03_0079

Principal Investigator: Kathleen Kraemer (Boston College)

Title: Fullerene Emission from Crystalline Silicate Sources: A FORCAST Investigation

Abstract: The infrared spectra of evolved stars are typically dominated by features from either carbon-rich grains and molecules or by oxygen-rich grains and molecules. Recently, the very large molecule buckminsterfullerene, C_60, has been detected, primarily around carbon-rich evolved objects such as post-AGB stars and planetary nebulae, but also from a small number of oxygen-rich sources. Thus, the physical conditions necessary to produce this molecule are not yet well understood. Our goal is to better constrain the physical conditions that are needed to for fullerene production and detection around evolved stars. In particular, we will examine a sample of 21 evolved stars in the Milky Way that are known to have crystalline silicate features in their infrared spectra, as these are the type of oxygen-rich source that fullerene have been detected in. We request 3.65 hours with the FORCAST grism on SOFIA to obtain 17.6-27.7 micron spectra of our targets, which covers the 18.9 micron fullerene emission feature.


Proposal ID: 03_0091

Principal Investigator: John Bally (University of Colorado)

Title: FORCAST Imaging and Spectroscopy of the mini-starburst in W43

Abstract: The W43 ‘mini-starburst’ region is one of the most luminous giant HII region / massive star formation complexes in the Galaxy and the closest analog of a forming super star cluster. These observations will help constrain the properties of massive star formation in a densely clustered environment and set the context for our understanding of starbursts and the formation of super-star clusters. The goals of this program are: [1] Search for massive, embedded protostars and clusters in the Z-shaped star-burst region which contains about 50 massive sub-mm / mm wavelength clumps of dense gas and which are saturated in the mid-IR Spitzer images. [2] Determine the SEDs, luminosities, and relative evolutionary stages of these protostars and clusters. [3] Investigate the structure of the warm mid-IR dust emission associated with the HII region, the surrounding PDR, and the massive protostars. [4] Obtain 191” x 2.4” long-slit spectra at three position to sample the full range of physical conditions in W43 from highly embedded protostars, compact HII regions, PDRs, the evolved HII region, and post-main-sequence objects. Three FORCAST grisms will provide nearly-complete spectra from 8.4 to 37.1 microns using three slit positions containing W43-MM1, MM3, and the IR source in the WR+OB cluster. These observations will build a multi-wavelength, high resolution picture of a Galactic ‘mini-starburst’ covering its entire spectral energy distribution for comparison to extragalactic starbursts.

Proposal ID: 03_0104

Principal Investigator: Gregory Sloan (Cornell University)

Title: An infrared spectral survey of Galactic carbon stars

Abstract: We propose to observe a sample of bright carbon stars in the Milky Way with the FORCAST grisms. These new infrared spectra will correct the biases in the Galactic sample observed with the SWS on the Infrared Space Observatory. The SWS sample is the only existing sample of Galactic carbon stars with sufficient wavelength coverage to measure the quantity of warm circumstellar dust, and the FORCAST grism mode provides our only means of obtaining similar spectra. Two key populations of carbon stars are poorly represented in the SWS sample: variables with the longest pulsation periods, and overtone pulsators. Our SOFIA sample will double the number of overtone pulators and increase the longest-period pulsators from four to 27. These observations will enable more robust comparisons of Galactic carbon stars with the samples of metal-poor carbon stars in the Magellanic Clouds and other Local Group dwarf galaxies obtained by the IRS on Spitzer. This step is vital for a proper understanding of the role of metallicity in the mass-loss and dust-formation processes in evolved stars.


Proposal ID: 03_0114

Principal Investigator: Margaret McAdam (University of Maryland)

Title: Degree of Alteration on Asteroids: Mapping water in the Asteroid Belt

Abstract: We propose to measure the water content of primitive asteroid surfaces through emissivity features in the mid-infrared using FORCAST on SOFIA. Our targets are distributed throughout the middle and outer asteroid belt, allowing us to map the distribution of water in this population. Using newly found spectral trends in a suite of aqueously altered meteorites, it is possible to identify the degree of aqueous alteration on the surfaces of dark asteroids remotely. The key measurements required are FORCAST spectra of 30 primitive asteroids, 12 of which are observable during SOFIA Cycle 3, using the grisms G111 and G227 covering 8.4-13.5 and 17.6-27.7 microns respectively. These wavelength regions have strong spectral features from phyllosilicates, hydrated minerals that are produced during aqueous alteration. The presence and positions of these features indicate the mineralogy of the surfaces of asteroids and additionally, the degree to which the asteroids are altered. The anticipated results are quantitative constraints on the water content of primitive asteroids as a function of location in the asteroids belt, and thus a step towards understanding the distribution of water in the early solar system.

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